1. Field of the Invention
The present invention relates to a direct flame impingement burner for heating metallic materials such as blanks, slabs, and the like.
2. Description of the Related Art
Direct flame impingement burners are used for heating various metallic materials. Instead of heating a volume of the atmosphere in, for example, a furnace, and thus heating a material indirectly, the flame impinges directly upon the surface of the material, thus heating it directly. That gives rise to better heat transfer efficiency from the burner to the material.
Such burners are commonly used in, for example, industrial furnaces for the continuous or discreet heating processing of metallic materials. They can also be used separately, for example when preheating or melting materials.
A typical direct flame impingement burner includes a nozzle, in turn including at least one fuel opening and one oxidant opening, from which fuel and oxidant are dispatched, respectively.
Such a typical direct flame impingement burner is fed with a gaseous fuel, for example natural gas, and a gaseous oxidant, for example oxygen, for the fuel and the oxidant, respectively. The burner includes fuel and oxidant nozzles that can be arranged at a distance from each other, in order to gain control over parameters such as combustion temperature, NOx content of combustion products, and the like.
However, in order to optimize the burner behavior arid efficiency in various applications, the respective nozzle openings for fuel and oxidant in the burner head can be arranged in a variety of ways. The choice of arrangement will, among other things, affect the chemical reaction surface between the fuel and oxidant.
Naturally, each nozzle opening needs to be supplied either with fuel or with oxidant. Thus, in an arrangement with several individual openings for both fuel and oxidant, there is a need for multiple supply piping. This is especially true in the common case in which control over the gas pressure in each individual opening is desired for control over the combustion characteristics. In order to fit the supply pipes, valves, and the like, the burner will have to be made quite bulky, something that constitutes a problem in terms of placement in a production line or in an industrial furnace. Also, the cost of production as well as the cost of maintenance of the burner both increase because of the many individual parts.
When heating metallic materials, it is often desired to heat the material uniformly across a larger part of the surface area of the material. For example, when continuously processing metal sheets, it is often desired to obtain a uniform heating profile across the whole width of the processed metal sheet, in order to avoid temperature gradients, and the like. When using direct flame impingement burners, there is therefore a need to use several direct flame impingement burners in conjunction, arranged side by side.
In the case when using several direct flame impingement burners, there is a problem in obtaining a uniform heating profile across all the individual direct flame impingement burners. Namely, in order to obtain such a uniform heating profile, all individual burners need to provide the same heating power to the material. Since the heating power of the direct flame impingement burner depends on the gas pressure of the fuel and the oxidant at each respective opening, those pressures need to be equal in corresponding nozzle openings over the whole range of individual direct flame impingement burners.
When using tubing or piping in order to supply each individual fuel or oxidant nozzle opening, besides the problem of bulkiness, it is difficult to obtain the desired equal gas pressures because of pressure drops that occur in the various parts of the tubing or piping, such as in individual tubes, pipes, valves, connections, and the like. Those pressure drops are often difficult to calculate beforehand, so practical experimentation is necessary in order to make the gas pressures equal between the various nozzle openings, which is costly in terms of time consumption. Also, changes in the piping, replacement of parts, and the like, will possibly affect the final nozzle opening gas pressures, making a recalibration necessary, which is also costly.
The present invention solves the above-described problems.